Automatic fabric drying machine and control means



y 6, 1965 P. G. HUGHE S 3,192,642

AUTOMATIC FABRIC DRYING MACHINE AND CONTROL MEANS Filed Nov. 6, 1961 3Sheets-Sheet 1 INVENTOR. PH\LI P e. HUGHES H as ATTORNEY July 6, 1965 P.e. HUGHES 3,192,642

AUTOMATIC FABRIC DRYING MACHINE AND CONTROL MEANS Filed NOV. 6, 1961 3sheetsrsheet 2 MPLIFIER 6 (,4, 5| .5 4 l AvA'A 58 s4 s9 56 53 S! II I kr17 s LLEI sucnaAL REFLECTED 5 DRY FAIRICS I00 1 1 5 l 5 l o w 29 3o 405'0 60 7o DRYtNG TIMI. m M\NUI'I.5

'4 or WATER RETENHON F l G 4 ENVELOPE oi VOLTAGE STANDING WAVESINVENTOR.

PHILIP G. HUGHES .40 MINUTES BY w P j f H \5 ATTORNEY AUTOMATIC FABRICDRYING MACHINE AND CONTROL MEANS Filed Nov. 6. 1961 P. G. HUGHES 'July6, 1965 3 Sheets-Sheet 3 FlG.7

Fias

INVENTOR. PHHJP G. HUGHES BY Q2 M H \S ATTORNEY United States PatentThis invention relates to an automatic fabric drying machine, and moreparticularly to an improved system in such machines for sensing when thefabrics therewithin are substantially dry and for accordinglyterminating further drying operations within the machine.

Many commercially produced fabric drying machines are provided withmeans for automatically terminating a drying cycle when the clothes aresubstantially dry, as opposed to the earlier approach of requiring thatthe operator estimates the drying time of the clothes and set a timeraccordingly. While a number of systems have been evolved for determiningwhen the clothes are dry and shutting oi the machine, a substantialdifiiculty in virtually all of them has been in the achievement of ahigh degree of sensitivity and accuracy as the clothes approach drynessso that the machine will be accurate in its determination and will tendneither to overdry nor to underdry clothes.

For this reason, it is an object of my invention to provide an improvedcontrol system for a fabric drying machine wherein the drying operationis automatically terminated in response to the elimination ofsubstantially all moisture from the fabrics in the machine.

A more specific object of my invention is to achieve the aforementionedgoal by the use of high frequency electromagnetic waves emitted into thefabric container.

Yet a more specific object of my invention is to achieve the desiredgoal of terminating the operation when the fabrics are dry by matchingthe wave length of the high frequency waves to the dimensions of theclothes container so that the container will reflect a predeterminedpart of the emitted waves when the clothes reach the desired conditionof dryness.

In one aspect of my invention I provide a fabric drying machine whichhas, in the usual manner, a substantially closed fabric container ofconductive material. This may, for instance, be a rotating tumbler ordrum formed of sheet metal. Suitable means are provided for drying thefabrics contained in the drum, and While these may assume any desiredform, the usual typical structure involves the application of heat tothe fabrics in the drum to evaporate the moisture in the fabrics, andthen some means for carrying off the evaporated moisture. I furtherprovide means for generating an electric current having a highfrequency, and I couple this generating means to a suitable structurepositioned so that it emits electromagnetic waves of high frequency intothe container.

The container is so proportioned to the frequency of the waves that thereflection of the waves from the container changes toward apredetermined pattern as the amount of moisture in the fabrics withinthe container decreases toward substantial dryness. Stated differently,wet fabrics, by the absorption and reflection of power by the moisturein the fabrics, modify the pattern of wave reflection from that whichexists when substantially all the power inflection is provided by thecontainer. As the fabrics dry, the modification of the wave patternbecomes less and less, approaching more closely to the predetermineddryness pattern as the moisture content of the fabrics decreases.Measuring means are provided to determine the pattern of reflection ofthe emitted waves, and when the measuring means determines that thereflection of the waves has assumed a predetermined $392,642 PatentedJuly 6, 1965 pattern it causes the drying means to be shut off toterminate drying within the machine. With this structure, a dryingoperation is automatically terminated as a direct function of the amountof moisture within the drum regardless of the type of fabric involved,and regardless of whether the moisture is deep within the fabrics or atthe surface of the fabrics.

The subject matter which I regard as my invention is particularlypointed out and distinctly claimed in the concluding portion of thisspecification. My invention, however, both as to organization and methodof operation, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconjunction with the accompanying drawings.

In the drawings,

FIGURE 1 is a side elevational view of a clothes dryer incorporating myimproved dryness control arrangement, the View being partly broken awayand partly sectionalized in order to illustrate details;

FIGURE 2 is a schematic illustration of my improved control system asused in the machine of FIGURE 1;

FIGURE 3 is a graph showing actual experimental results in a machine ofthe type described in FIGURES l and 2 for different types of clothesloads;

FIGURE 4 is another graph showing experimental results in a machine ofthe type described in FIGURES l and 2 for a typical clothes load;

FIGURE 5 is a fragmentary side elevational view of a clothes dryer ofthe general type shown in FIGURE 1 but which incorporates a secondembodiment of my improved dryness control arrangement;

FIGURE 6 is a fragmentary side elevational view of a clothes dryer ofthe general type shown in FIGURE 1 in which a third embodiment of myinvention is shown; and

FIGURE 7 is a fragmentary side elevational view of the front part of aclothes dryer of the general type shown in FIGURE 1 illustrating afourth embodiment of my invention.

Referring now to FIGURE 1, I have shown therein a domestic clothes dryer1 including a clothes tumbling con tainer or drum 2 and provided with asuitable outer casing or cabinet 3 which completely encloses the drum onall sides. The drum is mounted for rotation within cabinet 3 on asubstantially horizontal axis, and is generally cylindrical in shape,having a first outer cylindrical wall portion 4, second and thirdcylindrical outlet wall portions 5 and 6 located respectively adjacentthe ends of the drum, a back wall '7, and a front wall 8. The drum isformed of sheet metal; outer wall portions 4, 5 and 6 are formed ofimperforate sheet metal over their entire length, so that the entireouter shell of the basket is imperforate; on the interior surface ofcentral portion 4 there is provided a plurality of clothes tumbling ribs9 for causing the basket, when it rotates to move the clothes upwardlyand then drop them thereby continually to change the exposed surfaces ofthe fabric. Ribs g are preferably formed of non-conductive material, inthis particular embodiment, although appropriate design of the variouscomponents has been found to permit the use of a drum with ribs ofconductive material.

The front of drum 2 is rotatably supported within the outer casing 3 bymeans of a pair of idler roller wheels, one of which is shown by thenumeral 10, which are rotatably secured to the top of an upwardlyextending member 11. Member 11 is mounted at its bottom to the base 12of the machine. Rollers 10 are disposed beneath the drum on each sidethereof in contact with portion 6. The rear end of the drum receives itssupport from a roller wheel 13 which is positioned beneath porsasaeeetion of the drum in supporting and frictionally driving engagementtherewith.

Roller 13 is secured on a. shaft 14 supported in bearings 15. Shaft 14is secured to a pulley 16 which is driven from a belt 17 in turn poweredby a pulley 18 mounted on the end of a shaft 19 of an electric motor 2d.The motor, pulleys, and roller 13 are so proportioned to drum 2 and toeach other that drum 2 is rotated by roller 13 at the appropriate speedto provide tumbling action for mticles of clothing placed therein.

In order that a stream of drying air may be introduced into and passedthrough the clothes drum, the drum is provided with a central aperture21 in its front wall 8 and with a plurality of perforations 22 extendingin an annulus around back wall 7. Rigidly secured to the rear wall 23 ofeasing 5 by any desired means such as, for instance, welding at points24, is a bafile member 25 which has secured thereto heating means suchas an electric heater 25 appropriately insulated from the baffle member.Heating elements 26 may be annular in shape so as to be generallycoextensive with perforations 22 and drum 2. A baille member 27 isrigidly secured to the back wall 7 of the drum outside the ring ofperforations 22 and within the stationary baffle 25 so that an annularair inlet 28 is in effect formed by the baffles 25 and 27. Battle 27 isfurther provided with an annular series of spaced openings 29. In thismanner, a passage is formed for air to enter annular opening 26 betweenthe bafiles, pass over the eating elements 26, and through openings 29and perforations 22 into the interior of the drum 2.

In addition to the air guiding function, the baffles 25 and 2'7 helprollers it} and 13 to support the drum 2. Secured to the central portion3% of battle 27 is a bracket 31 to which in turn is secured a stub shaft32 substantially coaxially positioned relative to drum 2. The centralportion of battle 25 has a slot-like opening 34 formed therein. The slotis suitably formed (as is more fully described in copending applicationSerial No. 789,869

filed lanuary 29, 1959, now Patent No. 3,009,259, by I William F.Simpson and assigned to the same assignee as this invention) so as topermit stub shaft 32 a limited amount of movement in the verticaldirection but virtually no movement in the horizontal direction. Thus,the slight vertical motion of the drum which results from the tumblingof the clothes can be accommodated while at the same time undesirablehorizontal motion is afiirmatively prevented by engagement of stub shaft32 in slot The front opening 21 of the drum is substantially closed bymeans of a stationary bulkhead generally indicated by the numeral 35.Bulkhead 35 is made up of a number of adjacent members including theinner surface 36 of an access door 37 mounted on the dryer cabinet,stationary frame 38 for the door, the inner surface 39 of an exhaustduct 4d, and an annular flange 41 mounted on the frame 35 and on theduct wall. It will be noted that a suitable clearance is providedbetween the inner edge of the drum opening 21 and the edge of bulkhead35 so that there is no rubbing between the drum and the bulkhead duringrotation of the drum. In order to prevent any substantial air leakagethrough opening 21 between the interior and the exterior of the drum asuitable ring seal 32, preferably formed of felt-like material, issecured to flange 41 in sealing relationship with the exterior surfaceof drum wall 8.

Front opening 21, in addition to serving as part of the air flow paththrough the drum, also serves as a means whereby clothes may be loadedinto and unloaded from the drum. The door 37, whose inner surface formspart of the bulkhead closing the opening, is movably mounted on cabinet3 for movement between its closed and open positions; when the door isopen, the clothes may be insorted into or removed from the drum throughthe door Cil frame 38. It will be noted that the door includes an outerflat imperforate section t3, and an inwardly extending hollow section 44mounted on the fiat outer section. Hollow section 44 extends into thedoor frame 38 when the door is closed, and the door surface 36 whichcomprises part of the combination bulkhead is actually the inner wall ofthe hollow section. Surface 36, while it is preferably made up primarlyof sheet metal, includes a section 45 formed of some dielectric materialwhich is substantially rigid and formed to withstand the heat within thedryer. in this connection, the polypropylenes are one typical class ofsubstances which may be used. Directly behind the sheet of dielectricmaterial there is provided a metallic sheet-metal box-like member 46which is substantially enclosed on all sides except at its front whereit abuts sheet 45. This member 46, positioned in the door 37, forms animportant part of my invention and will be further explained herebelowin connection with the system of FIGURE 2.

The air opening from the basket is provided by a perforated opening 47which may be formed in the inner wall 36 of the hollow door section 44.The bottom wall section of door section 4-4 and the adjacent wall ofdoor frame 38 are provided with aligned openings &8 and 49, opening 49providing the entrance to duct 46. As shown, a lint trap 50 which maycomprise a fine mesh bag is preferably positioned in duct 46 at opening49, the bag being supported by the door frame. Duct 4% leads to suitableair moving means which may, as shown, comprise a centrifiugal blower 51mounted on the shaft of motor 2% and thus driven directly by this motor.The outlet of blower 49 communicates with a suitable outlet duct (notshown) which is formed in the usual manner so as to permit passage ofair out of the machine 1. During operation of motor 20, the rotation ofblower 51 causes air to be drawn into cabinet 3 through any suitableopening such as that shown by the numeral 52 provided at the front ofthe machine. The air then passes through annular opening 28, over heaterelements 26, through openings 29 and perforations 22 into drum 2, andacross the drum, through perforated opening 47 and aligned openings 48and 49 into duct 40, and then through the blower 51 to theaforementioned outlet duct.

It will be understood at this point that a conventional timingmechanism, which is schematically shown by numeral 53 in FIGURE 2 but isnot otherwise shown, may be provided. Timer 53, through a suitablemanual control such as that shown at 54 in FIGURE 1, may be caused toinitiate the operation of motor 28 and the heating element 26 so thatair is drawn into the machine over the heater so as to be heated, andthen into the basket where it heats the clothes and thus causesevaporation of moisture from the clothes. The air is then exhaustedthrough the aforementioned path, carrying off with it the evaporatedmoisture.

As one important component of my invention, I provide, as shown inFIGURE 2, a circuit generally indicated by the numeral 55 for generatinga high frequency current power output. A relatively typical circuit isshown for achieving this purpose. It will be understood that the termhigh frequency is used in a non-technical sense, and includesfrequencies in both the VHF and UHF zones as they are technicallydefined (30 megacycles to 300 megacycles for Vl-IF and 300 megacycles to3000 megacycles for UHF). The circuit includes a suitable transistor 56having a base 57, an emitter 5S, and a collector 59. A feed backcapacitor 60 is connected across the emitter and the collector so as toprovide capacitive feed back from the collector to the emitter. Thecollector 59 of transistor 56 is connected to a resonant circuit 61which includes an inductive loop 62, and a tuning capacitor 63 connectedacross the inductive loop. Power input to the emitter may be providedfrom any source of DC. power which, in the present case, is shownschematically for the sake of simplicity in the form of a battery 63a.The circuit further includes suitable dropping resistors 64 and 65, abias resistor 66 and bypass capacitors 67 and 68 having one sideconnected to ground 69.

For the particular conventional circuit shown, it has been found that agermanium mesa transistor such as Model No. 2Nl405 manufactured by TexasInstruments, Inc., may be used for transistor 56 in connection with a 12volt source of DC. power as typified by battery 63a. In this circuit,suitable values for resistors 64-, 65 and 66 are 1,000 ohrns, 2,000 ohmsand 10,000 ohms respectively. The two bypass capacitors 6'7 and 68 maybe on the order of 100 picofarads, and the feed back ca pacitor 60 maybe on the order of 1 picofarad. The tuning capacitor 63 may be variablebetween values of 1 to picofarads thereby to provide output wavefrequencies on the order of 250 megacycles to 1,000 megacycies.

The generating circuit 55 described hereabove may be coupledto asuitable transmission line member 70 by any suitable means. In thepresent case, the coupling means is shown as a tap 71 on the loop 62,but it will be understood that any other type of coupling, such asinductive or capacitive, may be used.

A downwardly extending probe portion 75 of structure 70 is providedextending through a small opening 76 into sheet metal member 46. The boxmember 46 is so formed that its back surface 77 is spaced as closely asopssible to one quarter wave length from the probe 75. It is well knownthat the wave length (X) may readily be found by dividing the speed oflight by the frequency (f), i.e., the formula This formula shows that atfrequencies below 900 megacycles, the wave length exceeds 33centimeters, and in the particular structure shown the door will notnormally have a thickness suitable to provide the M4 spacing. Therefore,as can be seen in FIGURE 1, probe 75 is located as far forward towardthe sheet 45 as possible so as to leave the maximum distance betweenprobe 75 and the back wall 77 of member 46. With this arrangement,member 46 in effect forms a guide for the waves which emanate from theprobe 75, propagating them into the drum 2. The wave guide 46 furtherhas its side walls 73 each preferably spaced laterally at least onequarter wave length from the downwardly extending probe 75 for thepurpose of avoiding excessive attentuation of the electromagnetic waveemission from the probe 75.

The equipment thus far described in connected with FIGURE 2 is providedfor the purpose of causing power in the form of high frequencyelectromagnetic waves to emanate from probe 75 and be guided by the waveguide 46 into the drum 2 which, in the terminology of microwavetechnology, forms, cavity in that it is a dielectric region of arbitraryform entirely enclosed by conducting walls. In this connection, it willbe understood that the small openings which are provided within the drum2 to permit air circuation into and out of the drum may in effect beignored for the purpose of considering the drum to be entirely enclosedby conductive walls.

When a cavity is excited by electromagnetic waves whose length is shortcompared to the dimensions of the cavity, resonance may be found in thevicinity of many frequencies due to reflections from the walls of thecavity which cause standing waves to be produced in the electromagneticfields inside the cavity. Also, standing waves of voltage andcurrentwill be found in the transmission line that feeds the cavity resonator(or probe).

This resonance effect is obtained when the space within drum 2 is fullyoccupied by substantially low loss dielectric material such as air ordry fabrics. However, when wet fabrics are being tumbled in the drum 2,they represent a poor insulator, that is, rather than being a high gradedielectric they represent a lossy dielectric. The

meter per sec.

presence of wet fabrics therefore results in absorption and reflectionof a very substantial part of the emitted power by the water; when thisoccurs, the waves do not reflect off the surfaces of the drum so as tohave the anticipated effect on the emitted waves. the presence of wetfabrics within the cavity provides a substantial difference in thereflective action on the emitted waves from that which might normally beexpected from the reflected waves.

It will be seen from the foregoing that, when the pat tern of wavereflection for dry clothes within drum 2 has been determined, it is thenonly necessary to provide suitable means which, in response toattainment of that pattern of reflection, will then cause termination ofthe drying operation. While this may be done in several ways, I preferto measure the fluctuations of the voltage standing wave in thetransmission line 70 coupling the generator circuit 55 to the probe 75.This may be measured by suitable connection of a crystal diode 79 tomember 70 at a suitable location experimentally determined. A signal isthen passed by diode 79, as shown, to an amplifier which may be entirelyconventional and is therefore shown simply by the box 80. Amplifier 80has a pair of output terminals 81 and 82 across which a relay coil 83 isconnected. When the signal output passed by rectifier 79 reaches apredetermined level, the relay 33 is energized, closing its associatedswitch 84 and thereby energizing the aforementioned timer motor 53. Thetimer motor may then provide a few more minutes of heating to insurebone dryness if such is desired, or may provide a cool-down periodduring-which the motor 20 operates and the heaters do not. These areconventional aspects of automatic drying machines and, being well knownin the art, are therefore not further described herewithin. Of course,in the event appropriate sensitivity or time delays are incorporated inthe system, the predetermined pattern of reflection which shows that theclothes are dry may cause termination of the heating operationimmediately without any further operation of the machine 1.

By using a system substantially in accordance with the abovedescription, excellent control of fabric dryness has been achievedusing, experimentally, mc., 375 mc., 500 mc., 780 mc. and 915 mc. Thesefrequencies thus represent typical values which may be used, although itwill be understood that my invention is not limited by thesefrequencies, and that other frequencies, including both higher and lowerones, may be found appropriate in particular instances.

To illustrate one example of my invention, there are shown in FIGURE 3,in graph form, the results of drying different clothes loads in a drum18 inches deep and 25% inches in diameter, wherein a 9-15 mc. signal wasbeing emitted and suitable equipment was being used to measure thedegree, or level, of reflection of the signal.

7 Curve A reprsents a 3% pound load of synthetic fabrics,

Curve B is a 6 pound stuffer load (uniformly sized pieces of thin cottonfabric), Curve C is a 6 pound standard AHLMA load (a mixed load ofcottons including a sheet, towels, shirts, etc. representing a typicalfamily load), and Curve D is a 13 /2 pound bath mat load. It can be seenthat, for the three loads which were fully dried (Curves A, B and D),virtually the same percent reflection indicated bone dryness, and that,for a lesser percentage reflection, a slight degree of dampness (CurveC) is present. Thus, with the knowledge that in this particular systemabout 80% reflection means dryness, conventional controls may beprovided to give either dryness or any desired limited degree ofdampness at the end of a cycle.

A further understanding of the operation of my inven tion can beattained by reference to FIGURE 4, which represents test resultsobtained in the complete drying of a 6 pound AHLMA load in a drum of thedimensions described and again with a field of 915 mc. As has beenstated, it is not necessary to use the level of reflection In otherwords,

as the criterion, as was done in connection with the test runsillustrated in FIGURE 3. Rather, as shown in FIG- URE 4, otherreflection patterns such as the magnitude of the standing wave, whichrepresents the voltage fluctuation during drum rotation, may be measuredwith the knowledge that the magnitude of the fluctuations decreases to apredetermined level when the clothes are dry. This type of measurementis easily made with the connections shown in FIGURES 1 and 2 and alsorepresents an accurate reflection of the condition of the clothes as todryness. In this respect it will be noted that two separate functionsare plotted along the ordinate; the abscissa represents time in minutes,while both (1) percent Water retention by the fabrics, and (2) thevoltage standing wave envelope, or magniture of voltage fluctuation, areplotted along the ordinate.

It can been seen that the voltage fluctuation remains at a high level aslong as a substantial amount of liquid is retained in the clothes. Then,when the liquid retention decreases to 15 percent, the voltagefluctuation starts to decrease, and this decrease continues until awater retention of 5% is reached. Thus, as the clothes approach dryness,the system actually increases in sensitivity over that which it had whenthere was a substantial amount of water in the clothes. in other words,the fluctuations remain substantially constant throughout the wide rangewhen the clothes are quite wet, but decrease quite steeply as dryness isapproached so that in the area of dryness and minor dampness there ishigh sensitivity. This is most desirable in a system intended to measurethe dryness of fabrics and shut off a machine in response thereto.

While the level of reflection in the drum and the magnitude of thevoltage standing wave have been shown as two useful reflection patternsserving as measuring sticks, it will be understood that the inventionencompasses any of the conventional means of measuring the pattern ofthe standing waves or the modification of power requirements. Thus, forinstance, rather than measuring the voltage standing wave in thetransmission line, as has been done in the present case, the ratio ofinput to output, or the amount of power being required by the generatoralso serve as indications of Whether and to what degree the waves arebeing absorbed and reflected by water rather than reflected by the drumwalls. Thus, the power requirements of the circuit 55 could be measuredand also provide the intelligence as to the wave reflection pattern.Another system that could be used is to match the impedance of the dryclothes load so that with dry clothes there is very little reflection,and with wet clothes 2. larger reflection. In other words, what isprovided, in the board sense, is a change that is indicative of thewater content of the clothes in the region near dryness.

All of these phenomena, or indicia of phenomena, could be used .toprovide a signal which in turn could be amplified to achieve a controlfunction. Also, of course, any desired wave generating arrangement couldbe used rather than the one specifically shown to illustrate theinvention.

It will further be understood that, while as described the introductionof the electromagnetic field into the drum cavity has been effected bymeans of a probe positioned in the door of the machine together with awave guide for sending the field into the cavity, it will readily occurto those skilled in the art that a probe may be insorted into the cavityitself; this would eliminate the need for a particular structure such asbox or guide 46 to guide the field into the cavity.

In this connection, in FIGURE 5 there is shown in enlarged form a drumstructure wherein the back wall '7 of a typical drum, like that ofFIGURE 1, includes the supporting bracket 31 and the stub shaft 32extending through opening 34. In this case, the stub shaft is madehollow with an opening 89 extending therethrough to permit the entranceof a probe 81. It will be understood that while it is not shown, theprobe 81 is coupled to a w suitable generating circuit in the samemanner as discussed in connection with the structure of FIGURES 1 and 2.With the probe extending directly into the cavity formed by the drum,the need for a wave guide in order to direct the electromagnetic fieldinto the drum is obviated.

Of course, in order to prevent the fabrics within the drum from becomingtangled on the extending probe, a suitable cover 82 of dielectricmaterial may be provided, which extends smoothly from wall 7 so as toentirely enclose the probe 81, it being understood that clothes willslide off part 82 Without any problem. With part 32 made of a suitabledielectric material, it will be understood that the probe 81 is withinthe drum cavity in the true sense of the word, and that the member 82merely becomes another factor to be dealth with in providing the levelat which the signal used will cause the drying cycle to be ended.

Yet another means of introducing the field so as to excite the cavityformed by the drum is shown in FIG- URE 6, wherein it is shown that thetumbling ribs 9 are formed of plastic or non-conductive material, with aconductive loop 83 being positioned within at least one of the ribs soas to excite the cavity. In this case, of course, some suitable slipring arrangement would be desirable in order to provide the necessarypower to the generating circuit, but the details of such an arrangementwill readily be apparent to those skilled in the art.

Yet a further structure, shown in FIGURE 7 and high ly suitable in thosecases Where the dryer door is of limited thickness, is the provision ofa probe 84 suitably covered by a smooth member 85 of dielectric materialsecured to the inside surface of the door. This structure is verysimilar to that discussed in connection with FIG- URE 5, in that astraight sationary probe provides the necessary excitation within thecavity to effect a dryness measurement.

It can be seen from the foreging that my invention provides a controlsystem for a drying machine wherein the dryness of the fabric within thecontainer is measured directly by virtue of the changing dielectric andenergy absorbing qualities of the fabrics as they become dried.

While in accordance with the patent statutes I have described what atpresent is considered to be the preferred embodiment of my invention, itwill be obvious to those skilled in the art that various changes andmodifications, including but not limited to those specifically mentionedabove, may be made therein without departing from the invention, and itis therefore aimed in the appended claims to cover all such equivalentvariations as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A fabric drying machine comprising: a substantially closed fabriccontainer of conductive material; means for drying fabric in saidcontainer; means for generating an electric current having a highfrequency; means coupled to said generating means and positioned to emitelectromagnetic waves of said high frequency into said container; meansfor measuring the extent to which the emitted waves are reflected fromsaid container, said container being proportioned to said high frequencyso that the reflection of said waves changes toward a predeterminedpattern as the amount of moisture in the fabrics in said containerdecrease toward substantial dryness of the fabrics; and means connectedto said measuring means and responsive to said predetermined pattern ofreflection to shut oil said drying means,

2. The apparatus defined in claim 1 wherein said means coupled to saidgenerating means includes a conductive probe member extending into saidcontainer, said measuring means also being coupled to said probe memberso as to measure the standing waves in said probe member.

3. A fabric drying machine comprising: a substantially closed fabriccontainer of conductive material; means for drying fabrics in saidcontainer; means for generating an electric current having a highfrequenc; at least part of said container being formed as a wave guidefor electromagnetic waves of said high frequency; means coupled to saidgenerating means for emitting electromagnetic waves of said highfrequency through said wave guide into said container; means formeasuring the extent to which the emitted waves are reflected from saidcontainer, said container being proportioned to said high frequency sothat the reflection of said Waves changes toward a predetermined patternas the amount of moisture in the fabrics in said container decreasestoward substantial dryness of the fabrics; and means connected to saidmeasuring means and responsive to said predetermined pattern ofreflection to shut 01f said drying means.

4. The apparatus defined in claim 3 wherein said means coupled to saidgenerating means includes a metallic probe member extending into saidwave guide, said measuring means also being coupled to said probe memberso as to measure the standing waves in said probe member and wave guide.

5. The apparatus defined in claim 1 wherein said container is in theform of a substantially cylindrical metallic drum rotatably mounted forrotation on a non-vertical axis thereby to effect tumbling of fabricswithin the drum.

6. A fabric drying machine comprising: a substantially closed fabriccontainer of conductive material comprising a substantially cylindricalmetallic drum having one open end for access purposes and mounted forrotation on a non-vertical axis; a cabinet enclosing said drum; and ametallic door in said cabinet arranged to engage said open end of saiddrum thereby to complete an enclosure therewith; means for dryingfabrics in said enclosure; means for generating an electric currenthaving a high frequency; said door having a portion thereof formed as awave guide for electromagnetic waves of said high frequency; meanscoupled to said generating means for emitting electromagnetic waves ofsaid high frequency through said wave guide into said enclosure; meansfor measuring the extent to which the emitted waves are reflected fromsaid enclosure, said enclosure being proportioned to said high frequencyso that the reflection of said waves changes toward a predeterminedpattern as the amount of moisture in the fabrics in said enclosuredecreases toward substantial dryness of the fabrics; and means connectedto said measuring means and responsive to said predetermined pattern ofreflection to shut off said drying means.

7. The apparatus defined in claim 1 wherein said means for dryingfabrics includes heating means positioned to heat the fabrics in saidcontainer, and means for removing the moisture evaporated from thefabrics, said means responsive to said predetermined pattern ofreflection being effective to cause said drying means to be shut off inresponse to said predetermined level of reflection.

8. The apparatus defined in claim 3 wherein said wave guide issubstantially rectangular in form, and said coupled means includes amember extending through a wall of said Wave guide thereinto.

9. The apparatus defined in claim 8 wherein said means for measuring theextent to Which the emitted waves are reflected includes a diodepositioned to measure the standing wave of the electromagnetic fieldwithin said container.

14 The apparatus defined in claim 1 including a timer mechanismeffective when started to toll a predetermined operation of said dryingmeans and thereupon stop operation of said drying means, said timerbeing started in response to said predetermined pattern of reflection.

11. A fabric drying machine comprising: a substantially closed fabriccontainer of conductive material comprising a substantially cylindricalmetallic drum having one open end for access purposes and mounted forrotation on a non-vertical axis; a cabinet enclosing said drum; and ametallic door in said cabinet arranged to engage said open end of saiddrum thereby to complete an enclosure therewith; means for dryingfabrics in said enclosure; means for generating an electric currenthaving a frequency; means coupled to said generating means and extendinginto said enclosure for emitting electromagnetic waves of said highfrequency into said enclosure; smooth means formed of dielectricmaterial covering said coupled means within said enclosure; means formeasuring the extent to which the emitted waves are reflected from saidenclosure, said enclosure being proportioned to said high frequency sothat the reflection of said waves changes toward a predetermined patternas the amount of moisture in the fabrics in said enclosure decreasestoward substantial dryness of the fabric; and means connected to saidmeasuring means and responsive to said predetermined pattern ofreflection to shut off said drying means.

12. The apparatus defined in claim 11 wherein said coupled-means extendsinto said enclosure through said door.

13. The apparatus defined in claim 11 wherein said coupled means extendsinto said enclosure through the end thereof opposite said open end.

14. The apparatus defined in claim 11 wherein said drum has clothestumbling ribs of non-conductive material formed therein and said coupledmeans extends into said drum within at least one of said ribs.

References titted by the Examiner UNITED STATES PATENTS 2,045,381 6/36Elberty 34-55 2,611,804 9/52 Zaleski 32458.5 2,729,786 1/56 Wild 32458.52,792,548 11/57 Hershberger 32458.5 2,882,610 4/59 Hughes 3445 3,034,0464/62 Sasaki 32458.5 3,079,552 2/63 Walker 32458.5

PERCY L. PATRICK, Primary Examiner.

NORMAN YUDKOFF, Examiner.

1. A FABRIC DRIVING MACHINE COMPRISING: A SUBSTANTIALLY CLOSED FABRICCONTAINER OF CONDUCTIVE MATERIAL; MEANS FOR DRYING FABRIC IN SAIDCONTAINER; MEANS FOR GENERATING AN ELECTRIC CURRENT HAVING A HIGHFREQUENCY; MEANS COUPLED TO SAID GENERATING MEANS AND POSITIONED TO EMITELECTROMAGNETIC WAVES OF SAID HIGH FREQUENCY INTO SAID CONTAINER; MEANSFOR MEASURING THE EXTENT TO WHICH THE EMITTED WAVES ARE REFLECTED FROMSAID CONTAINER, SAID CONTAINER BEING PROPORTIONED TO SAID HIGH FREQUENCYSO THAT THE REFLECTION OF SAID WAVES CHANGES TOWARD A PREDETERMINEDPATTERN AS THE AMOUNT OF MOISTURE IN THE FABRICS IN SAID CONTAINERDECREASE TOWARD SUBSTANTIAL DRYNESS OF THE FABRICS; AND MEANS CONNECTEDTO SAID MEASURING MEANS AND RESPONSIVE TO SAID PREDETERMINED PATTERN OFREFLECTION TO SHUT OFF SAID DRYING MEANS.